HRT study cancelled over cancer and stroke fears

More than 16,000 women participating in a study on hormone replacement therapy were abruptly told to stop taking their medication yesterday after US government scientists' findings suggested that the drugs significantly increased the risk of breast cancer, heart attacks, strokes and blood clots.

Oestrogen and progesterone are taken by millions of women worldwide to combat the symptoms of menopause, and many doctors believe that, used over many years, they also reduce the risk of heart disease and improve health.

But the study, funded by the government-run national institutes of health and scheduled to run for eight years, was called off this week after five years when the findings indicated that long term use of the leading American HRT drug, Prempro, increased a healthy woman's risk of breast cancer by 24%, stroke by 41% and heart attack by 29%.

Prempro is not marketed in Britain, but the versions of the drugs used are the same as in Premique, one of the leading UK brands. Six million HRT prescriptions were issued in England last year, according to the medicines control agency.

"This has huge implications," Malcolm Whitehead, director of the Menopause Clinic at King's College, London, said. "It means we may be going back to the late 1970s, where you are just going to use [HRT] for four or five years around the menopause for women who are very symptomatic. You just can't justify long term use with these indications."

Data from the 16,608 woman study suggest that for every 10,000 healthy women taking HRT, eight more will develop invasive breast cancer, seven more will have a heart attack, 18 more will suffer blood clots and eight more will have a stroke than among 10,000 healthy women not taking the treatment.

On the other hand, six fewer will develop colon cancer and five fewer will suffer hip fractures - but doctors agree there are better ways to prevent those specific problems.

The women involved, aged between 50 and 79, had been due to receive letters informing them of the results yesterday, but the news leaked to the media before the letters arrived. Half of them had been taking a placebo.

Wyeth, maker of the best-selling Prempro, said it was informing doctors of the findings.

Jacques Rossouw, the acting director of the study, said the researchers wanted "to get the word out to women and their doctors that long term use of this therapy could be harmful". But he said even shorter term use could have its risks: although the additional cancer risk did not appear until the fourth year of long term use, the risk of heart attack increased within the first year.

But Suzanne Fletcher and Graham Colditz, of the Harvard school of public health, urged calm. "We recommend that clinicians stop prescribing this combination for long term use," they wrote in an editorial on the website of the Journal of the American Medical Association, in which they called the results "unexpected and disquieting". But "the absolute risk of harm to an individual woman is very small".

The cancellation of the study is sure to stoke the years-long debate over HRT, which has been hailed as a counterbalance not only to the effects of menopause but of ageing and declining health in general. But in 1997 a study led by Valerie Beral at Oxford University found that HRT increased the risk of breast cancer by 25%.

The crucial question for British women is whether the data applies to other types of HRT, including oestrogen-only therapies taken by some women who have had hysterectomies, or to HRT administered via patches.

A spokesman for the UK industry-supported organisation HRT Aware said: "There is a vast array of HRT products prescribed in the UK. The WHI results should not be applied to any HRT product other than the one investigated in the trial."